1. Field of the Invention
The present invention relates to an apparatus for detecting a heartbeat synchronous wave produced from a living body in synchronization with heartbeat of the subject, through a probe which is adapted to be set on a body portion of the subject. Such apparatus comprise a pulse wave detecting apparatus, a pulse oxymeter, and an electrocardiograph, for example.
2. Related Art Statement
The detector probe of the above apparatus is used on, for example, a patient who is undergoing a surgical operation, for monitoring dynamic function of the circulatory system of the patient during the operation. In a surgical operation an electric knife is often used for cutting a body portion of a patient for the purpose of hemostasis and sterilization of the cut portion. When a high frequency electric current is applied to the electric knife, however, a fraction of the electric current flows to the detector probe via the patient's body, and adversely affects the detection of a heartbeat synchronous wave through the probe. Since such apparatus are adapted to utilize a considerably weak electric signal representative of the detected heartbeat synchronous wave, a high frequency electric current flowing to the detector probe results in mixing noise into the electric signal detected through the probe. The electric signal containing noise is not appropriate to use for the determination of a blood pressure or a blood oxygen saturation of the patient. A doctor or a nurse may see the inaccurate information determined based on the inappropriate signal and consequently have incorrect views on the dynamic function of the circulatory system of the patient undergoing the surgery.